<?php
/**
 * @version $Id: DifferenceEngine.php 24 2009-03-29 13:19:58Z der.el.kuku $
 * @package		EasyCreator
 * 
 * A PHP diff engine for phpwiki. (Taken from phpwiki-1.3.3)
 *
 * Additions by Axel Boldt for MediaWiki
 *
 * @copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @license  You may copy this code freely under the conditions of the GPL.
 */
define('USE_ASSERTS', function_exists('assert'));

class _DiffOp {
  var $type;
  var $orig;
  var $closing;

  function reverse() {
    trigger_error("pure virtual", E_USER_ERROR);
  }

  function norig() {
    return $this->orig ? sizeof($this->orig) : 0;
  }

  function nclosing() {
    return $this->closing ? sizeof($this->closing) : 0;
  }
}

class _DiffOp_Copy extends _DiffOp {
  var $type = 'copy';

  function _DiffOp_Copy ($orig, $closing = false) {
    if (!is_array($closing))
      $closing = $orig;
    $this->orig = $orig;
    $this->closing = $closing;
  }

  function reverse() {
    return new _DiffOp_Copy($this->closing, $this->orig);
  }
}

class _DiffOp_Delete extends _DiffOp {
  var $type = 'delete';

  function _DiffOp_Delete ($lines) {
    $this->orig = $lines;
    $this->closing = false;
  }

  function reverse() {
    return new _DiffOp_Add($this->orig);
  }
}

class _DiffOp_Add extends _DiffOp {
  var $type = 'add';

  function _DiffOp_Add ($lines) {
    $this->closing = $lines;
    $this->orig = false;
  }

  function reverse() {
    return new _DiffOp_Delete($this->closing);
  }
}

class _DiffOp_Change extends _DiffOp {
  var $type = 'change';

  function _DiffOp_Change ($orig, $closing) {
    $this->orig = $orig;
    $this->closing = $closing;
  }

  function reverse() {
    return new _DiffOp_Change($this->closing, $this->orig);
  }
}


/**
 * Class used internally by Diff to actually compute the diffs.
 *
 * The algorithm used here is mostly lifted from the perl module
 * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
 *   http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
 *
 * More ideas are taken from:
 *   http://www.ics.uci.edu/~eppstein/161/960229.html
 *
 * Some ideas are (and a bit of code) are from from analyze.c, from GNU
 * diffutils-2.7, which can be found at:
 *   ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
 *
 * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
 * are my own.
 *
 * @author Geoffrey T. Dairiki
 * @access private
 */
class _DiffEngine
{
  function diff ($from_lines, $to_lines) {
    $n_from = sizeof($from_lines);
    $n_to = sizeof($to_lines);

    $this->xchanged = $this->ychanged = array();
    $this->xv = $this->yv = array();
    $this->xind = $this->yind = array();
    unset($this->seq);
    unset($this->in_seq);
    unset($this->lcs);

    // Skip leading common lines.
    for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
      if ($from_lines[$skip] != $to_lines[$skip])
        break;
      $this->xchanged[$skip] = $this->ychanged[$skip] = false;
    }
    // Skip trailing common lines.
    $xi = $n_from; $yi = $n_to;
    for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
      if ($from_lines[$xi] != $to_lines[$yi])
        break;
      $this->xchanged[$xi] = $this->ychanged[$yi] = false;
    }

    // Ignore lines which do not exist in both files.
    for ($xi = $skip; $xi < $n_from - $endskip; $xi++)
      $xhash[$from_lines[$xi]] = 1;
    for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
      $line = $to_lines[$yi];
      if ( ($this->ychanged[$yi] = empty($xhash[$line])) )
        continue;
      $yhash[$line] = 1;
      $this->yv[] = $line;
      $this->yind[] = $yi;
    }
    for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
      $line = $from_lines[$xi];
      if ( ($this->xchanged[$xi] = empty($yhash[$line])) )
        continue;
      $this->xv[] = $line;
      $this->xind[] = $xi;
    }

    // Find the LCS.
    $this->_compareseq(0, sizeof($this->xv), 0, sizeof($this->yv));

    // Merge edits when possible
    $this->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
    $this->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);

    // Compute the edit operations.
    $edits = array();
    $xi = $yi = 0;
    while ($xi < $n_from || $yi < $n_to) {
      USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
      USE_ASSERTS && assert($xi < $n_from || $this->ychanged[$yi]);

      // Skip matching "snake".
      $copy = array();
      while ( $xi < $n_from && $yi < $n_to
          && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
        $copy[] = $from_lines[$xi++];
        ++$yi;
      }
      if ($copy)
        $edits[] = new _DiffOp_Copy($copy);

      // Find deletes & adds.
      $delete = array();
      while ($xi < $n_from && $this->xchanged[$xi])
        $delete[] = $from_lines[$xi++];

      $add = array();
      while ($yi < $n_to && $this->ychanged[$yi])
        $add[] = $to_lines[$yi++];

      if ($delete && $add)
        $edits[] = new _DiffOp_Change($delete, $add);
      elseif ($delete)
        $edits[] = new _DiffOp_Delete($delete);
      elseif ($add)
        $edits[] = new _DiffOp_Add($add);
    }
    return $edits;
  }


  /**
   * Divide the Largest Common Subsequence (LCS) of the sequences
   * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
   * sized segments.
   *
   * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an
   * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
   * sub sequences.  The first sub-sequence is contained in [X0, X1),
   * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
   * that (X0, Y0) == (XOFF, YOFF) and
   * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
   *
   * This function assumes that the first lines of the specified portions
   * of the two files do not match, and likewise that the last lines do not
   * match.  The caller must trim matching lines from the beginning and end
   * of the portions it is going to specify.
   */
  function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks) {
  $flip = false;

  if ($xlim - $xoff > $ylim - $yoff) {
    // Things seems faster (I'm not sure I understand why)
      // when the shortest sequence in X.
      $flip = true;
    list ($xoff, $xlim, $yoff, $ylim)
    = array( $yoff, $ylim, $xoff, $xlim);
    }

  if ($flip)
    for ($i = $ylim - 1; $i >= $yoff; $i--)
    $ymatches[$this->xv[$i]][] = $i;
  else
    for ($i = $ylim - 1; $i >= $yoff; $i--)
    $ymatches[$this->yv[$i]][] = $i;

  $this->lcs = 0;
  $this->seq[0]= $yoff - 1;
  $this->in_seq = array();
  $ymids[0] = array();

  $numer = $xlim - $xoff + $nchunks - 1;
  $x = $xoff;
  for ($chunk = 0; $chunk < $nchunks; $chunk++) {
    if ($chunk > 0)
    for ($i = 0; $i <= $this->lcs; $i++)
      $ymids[$i][$chunk-1] = $this->seq[$i];

    $x1 = $xoff + (int)(($numer + ($xlim-$xoff)*$chunk) / $nchunks);
    for ( ; $x < $x1; $x++) {
        $line = $flip ? $this->yv[$x] : $this->xv[$x];
        if (empty($ymatches[$line]))
      continue;
    $matches = $ymatches[$line];
        reset($matches);
    while (list ($junk, $y) = each($matches))
      if (empty($this->in_seq[$y])) {
      $k = $this->_lcs_pos($y);
      USE_ASSERTS && assert($k > 0);
      $ymids[$k] = $ymids[$k-1];
      break;
          }
    while (list ($junk, $y) = each($matches)) {
      if ($y > $this->seq[$k-1]) {
      USE_ASSERTS && assert($y < $this->seq[$k]);
      // Optimization: this is a common case:
      //  next match is just replacing previous match.
      $this->in_seq[$this->seq[$k]] = false;
      $this->seq[$k] = $y;
      $this->in_seq[$y] = 1;
          }
      else if (empty($this->in_seq[$y])) {
      $k = $this->_lcs_pos($y);
      USE_ASSERTS && assert($k > 0);
      $ymids[$k] = $ymids[$k-1];
          }
        }
      }
    }

  $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
  $ymid = $ymids[$this->lcs];
  for ($n = 0; $n < $nchunks - 1; $n++) {
    $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
    $y1 = $ymid[$n] + 1;
    $seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
    }
  $seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);

  return array($this->lcs, $seps);
  }

  function _lcs_pos ($ypos) {
  $end = $this->lcs;
  if ($end == 0 || $ypos > $this->seq[$end]) {
    $this->seq[++$this->lcs] = $ypos;
    $this->in_seq[$ypos] = 1;
    return $this->lcs;
    }

  $beg = 1;
  while ($beg < $end) {
    $mid = (int)(($beg + $end) / 2);
    if ( $ypos > $this->seq[$mid] )
    $beg = $mid + 1;
    else
    $end = $mid;
    }

  USE_ASSERTS && assert($ypos != $this->seq[$end]);

  $this->in_seq[$this->seq[$end]] = false;
  $this->seq[$end] = $ypos;
  $this->in_seq[$ypos] = 1;
  return $end;
  }

  /**
   * Find LCS of two sequences.
   *
   * The results are recorded in the vectors $this->{x,y}changed[], by
   * storing a 1 in the element for each line that is an insertion
   * or deletion (ie. is not in the LCS).
   *
   * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
   *
   * Note that XLIM, YLIM are exclusive bounds.
   * All line numbers are origin-0 and discarded lines are not counted.
   */
  function _compareseq ($xoff, $xlim, $yoff, $ylim) {
  // Slide down the bottom initial diagonal.
  while ($xoff < $xlim && $yoff < $ylim
         && $this->xv[$xoff] == $this->yv[$yoff]) {
    ++$xoff;
    ++$yoff;
    }

  // Slide up the top initial diagonal.
  while ($xlim > $xoff && $ylim > $yoff
         && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
    --$xlim;
    --$ylim;
    }

  if ($xoff == $xlim || $yoff == $ylim)
    $lcs = 0;
  else {
    // This is ad hoc but seems to work well.
    //$nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
    //$nchunks = max(2,min(8,(int)$nchunks));
    $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
    list ($lcs, $seps)
    = $this->_diag($xoff,$xlim,$yoff, $ylim,$nchunks);
    }

  if ($lcs == 0) {
    // X and Y sequences have no common subsequence:
    // mark all changed.
    while ($yoff < $ylim)
    $this->ychanged[$this->yind[$yoff++]] = 1;
    while ($xoff < $xlim)
    $this->xchanged[$this->xind[$xoff++]] = 1;
    }
  else {
    // Use the partitions to split this problem into subproblems.
    reset($seps);
    $pt1 = $seps[0];
    while ($pt2 = next($seps)) {
    $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
    $pt1 = $pt2;
      }
    }
  }

  /**
   * Adjust inserts/deletes of identical lines to join changes
   * as much as possible.
   *
   * We do something when a run of changed lines include a
   * line at one end and has an excluded, identical line at the other.
   * We are free to choose which identical line is included.
   * `compareseq' usually chooses the one at the beginning,
   * but usually it is cleaner to consider the following identical line
   * to be the "change".
   *
   * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
   */
  function _shift_boundaries ($lines, &$changed, $other_changed) {
  $i = 0;
  $j = 0;

  USE_ASSERTS && assert('sizeof($lines) == sizeof($changed)');
  $len = sizeof($lines);
  $other_len = sizeof($other_changed);

  while (1) {
    /*
     * Scan forwards to find beginning of another run of changes.
     * Also keep track of the corresponding point in the other file.
     *
     * Throughout this code, $i and $j are adjusted together so that
     * the first $i elements of $changed and the first $j elements
     * of $other_changed both contain the same number of zeros
     * (unchanged lines).
     * Furthermore, $j is always kept so that $j == $other_len or
     * $other_changed[$j] == false.
     */
    while ($j < $other_len && $other_changed[$j])
    $j++;

    while ($i < $len && ! $changed[$i]) {
    USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
    $i++; $j++;
    while ($j < $other_len && $other_changed[$j])
      $j++;
      }

    if ($i == $len)
    break;

    $start = $i;

    // Find the end of this run of changes.
    while (++$i < $len && $changed[$i])
    continue;

    do {
    /*
     * Record the length of this run of changes, so that
     * we can later determine whether the run has grown.
     */
    $runlength = $i - $start;

    /*
     * Move the changed region back, so long as the
     * previous unchanged line matches the last changed one.
     * This merges with previous changed regions.
     */
    while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
      $changed[--$start] = 1;
      $changed[--$i] = false;
      while ($start > 0 && $changed[$start - 1])
      $start--;
      USE_ASSERTS && assert('$j > 0');
      while ($other_changed[--$j])
      continue;
      USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
        }

    /*
     * Set CORRESPONDING to the end of the changed run, at the last
     * point where it corresponds to a changed run in the other file.
     * CORRESPONDING == LEN means no such point has been found.
     */
    $corresponding = $j < $other_len ? $i : $len;

    /*
     * Move the changed region forward, so long as the
     * first changed line matches the following unchanged one.
     * This merges with following changed regions.
     * Do this second, so that if there are no merges,
     * the changed region is moved forward as far as possible.
     */
    while ($i < $len && $lines[$start] == $lines[$i]) {
      $changed[$start++] = false;
      $changed[$i++] = 1;
      while ($i < $len && $changed[$i])
      $i++;

      USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
      $j++;
      if ($j < $other_len && $other_changed[$j]) {
      $corresponding = $i;
      while ($j < $other_len && $other_changed[$j])
        $j++;
          }
        }
      } while ($runlength != $i - $start);

    /*
     * If possible, move the fully-merged run of changes
     * back to a corresponding run in the other file.
     */
    while ($corresponding < $i) {
    $changed[--$start] = 1;
    $changed[--$i] = 0;
    USE_ASSERTS && assert('$j > 0');
    while ($other_changed[--$j])
      continue;
    USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
      }
    }
  }
}

/**
 * Class representing a 'diff' between two sequences of strings.
 */
class Diff
{
  var $edits;

  /**
   * Constructor.
   * Computes diff between sequences of strings.
   *
   * @param $from_lines array An array of strings.
   *      (Typically these are lines from a file.)
   * @param $to_lines array An array of strings.
   */
  function Diff($from_lines, $to_lines) {
    $eng = new _DiffEngine;
    $this->edits = $eng->diff($from_lines, $to_lines);
    //$this->_check($from_lines, $to_lines);
  }

  /**
   * Compute reversed Diff.
   *
   * SYNOPSIS:
   *
   *  $diff = new Diff($lines1, $lines2);
   *  $rev = $diff->reverse();
   * @return object A Diff object representing the inverse of the
   *          original diff.
   */
  function reverse () {
  $rev = $this;
    $rev->edits = array();
    foreach ($this->edits as $edit) {
      $rev->edits[] = $edit->reverse();
    }
  return $rev;
  }

  /**
   * Check for empty diff.
   *
   * @return bool True iff two sequences were identical.
   */
  function isEmpty () {
    foreach ($this->edits as $edit) {
      if ($edit->type != 'copy')
        return false;
    }
    return true;
  }

  /**
   * Compute the length of the Longest Common Subsequence (LCS).
   *
   * This is mostly for diagnostic purposed.
   *
   * @return int The length of the LCS.
   */
  function lcs () {
  $lcs = 0;
    foreach ($this->edits as $edit) {
      if ($edit->type == 'copy')
        $lcs += sizeof($edit->orig);
    }
  return $lcs;
  }

  /**
   * Get the original set of lines.
   *
   * This reconstructs the $from_lines parameter passed to the
   * constructor.
   *
   * @return array The original sequence of strings.
   */
  function orig() {
    $lines = array();

    foreach ($this->edits as $edit) {
      if ($edit->orig)
        array_splice($lines, sizeof($lines), 0, $edit->orig);
    }
    return $lines;
  }

  /**
   * Get the closing set of lines.
   *
   * This reconstructs the $to_lines parameter passed to the
   * constructor.
   *
   * @return array The sequence of strings.
   */
  function closing() {
    $lines = array();

    foreach ($this->edits as $edit) {
      if ($edit->closing)
        array_splice($lines, sizeof($lines), 0, $edit->closing);
    }
    return $lines;
  }

  /**
   * Check a Diff for validity.
   *
   * This is here only for debugging purposes.
   */
  function _check ($from_lines, $to_lines) {
    if (serialize($from_lines) != serialize($this->orig()))
      trigger_error("Reconstructed original doesn't match", E_USER_ERROR);
    if (serialize($to_lines) != serialize($this->closing()))
      trigger_error("Reconstructed closing doesn't match", E_USER_ERROR);

    $rev = $this->reverse();
    if (serialize($to_lines) != serialize($rev->orig()))
      trigger_error("Reversed original doesn't match", E_USER_ERROR);
    if (serialize($from_lines) != serialize($rev->closing()))
      trigger_error("Reversed closing doesn't match", E_USER_ERROR);


    $prevtype = 'none';
    foreach ($this->edits as $edit) {
      if ( $prevtype == $edit->type )
        trigger_error("Edit sequence is non-optimal", E_USER_ERROR);
      $prevtype = $edit->type;
    }

    $lcs = $this->lcs();
    trigger_error("Diff okay: LCS = $lcs", E_USER_NOTICE);
  }
}

/**
 * FIXME: bad name.
 */
class MappedDiff
extends Diff
{
  /**
   * Constructor.
   *
   * Computes diff between sequences of strings.
   *
   * This can be used to compute things like
   * case-insensitve diffs, or diffs which ignore
   * changes in white-space.
   *
   * @param $from_lines array An array of strings.
   *  (Typically these are lines from a file.)
   *
   * @param $to_lines array An array of strings.
   *
   * @param $mapped_from_lines array This array should
   *  have the same size number of elements as $from_lines.
   *  The elements in $mapped_from_lines and
   *  $mapped_to_lines are what is actually compared
   *  when computing the diff.
   *
   * @param $mapped_to_lines array This array should
   *  have the same number of elements as $to_lines.
   */
  function MappedDiff($from_lines, $to_lines,
            $mapped_from_lines, $mapped_to_lines) {

    assert(sizeof($from_lines) == sizeof($mapped_from_lines));
    assert(sizeof($to_lines) == sizeof($mapped_to_lines));

    $this->Diff($mapped_from_lines, $mapped_to_lines);

    $xi = $yi = 0;
    for ($i = 0; $i < sizeof($this->edits); $i++) {
      $orig = &$this->edits[$i]->orig;
      if (is_array($orig)) {
        $orig = array_slice($from_lines, $xi, sizeof($orig));
        $xi += sizeof($orig);
      }

      $closing = &$this->edits[$i]->closing;
      if (is_array($closing)) {
        $closing = array_slice($to_lines, $yi, sizeof($closing));
        $yi += sizeof($closing);
      }
    }
  }
}

/**
 * A class to format Diffs
 *
 * This class formats the diff in classic diff format.
 * It is intended that this class be customized via inheritance,
 * to obtain fancier outputs.
 */
class DiffFormatter
{
  /**
   * Number of leading context "lines" to preserve.
   *
   * This should be left at zero for this class, but subclasses
   * may want to set this to other values.
   */
  var $leading_context_lines = 0;

  /**
   * Number of trailing context "lines" to preserve.
   *
   * This should be left at zero for this class, but subclasses
   * may want to set this to other values.
   */
  var $trailing_context_lines = 0;

  /**
   * Format a diff.
   *
   * @param $diff object A Diff object.
   * @return string The formatted output.
   */
  function format($diff) {

    $xi = $yi = 1;
    $block = false;
    $context = array();

    $nlead = $this->leading_context_lines;
    $ntrail = $this->trailing_context_lines;

    $this->_start_diff();

    foreach ($diff->edits as $edit) {
      if ($edit->type == 'copy') {
        if (is_array($block)) {
          if (sizeof($edit->orig) <= $nlead + $ntrail) {
            $block[] = $edit;
          }
          else{
            if ($ntrail) {
              $context = array_slice($edit->orig, 0, $ntrail);
              $block[] = new _DiffOp_Copy($context);
            }
            $this->_block($x0, $ntrail + $xi - $x0,
                    $y0, $ntrail + $yi - $y0,
                    $block);
            $block = false;
          }
        }
        $context = $edit->orig;
      }
      else {
        if (! is_array($block)) {
          $context = array_slice($context, sizeof($context) - $nlead);
          $x0 = $xi - sizeof($context);
          $y0 = $yi - sizeof($context);
          $block = array();
          if ($context)
            $block[] = new _DiffOp_Copy($context);
        }
        $block[] = $edit;
      }

      if ($edit->orig)
        $xi += sizeof($edit->orig);
      if ($edit->closing)
        $yi += sizeof($edit->closing);
    }

    if (is_array($block))
      $this->_block($x0, $xi - $x0,
              $y0, $yi - $y0,
              $block);

    return $this->_end_diff();
  }

  function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
    $this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
    foreach ($edits as $edit) {
      if ($edit->type == 'copy')
        $this->_context($edit->orig);
      elseif ($edit->type == 'add')
        $this->_added($edit->closing);
      elseif ($edit->type == 'delete')
        $this->_deleted($edit->orig);
      elseif ($edit->type == 'change')
        $this->_changed($edit->orig, $edit->closing);
      else
        trigger_error("Unknown edit type", E_USER_ERROR);
    }
    $this->_end_block();
  }

  function _start_diff() {
    ob_start();
  }

  function _end_diff() {
    $val = ob_get_contents();
    ob_end_clean();
    return $val;
  }

  function _block_header($xbeg, $xlen, $ybeg, $ylen) {
    if ($xlen > 1)
      $xbeg .= "," . ($xbeg + $xlen - 1);
    if ($ylen > 1)
      $ybeg .= "," . ($ybeg + $ylen - 1);

    return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
  }

  function _start_block($header) {
    echo $header;
  }

  function _end_block() {
  }

  function _lines($lines, $prefix = ' ') {
    foreach ($lines as $line)
      echo "$prefix $line\n";
  }

  function _context($lines) {
    $this->_lines($lines);
  }

  function _added($lines) {
    $this->_lines($lines, ">");
  }
  function _deleted($lines) {
    $this->_lines($lines, "<");
  }

  function _changed($orig, $closing) {
    $this->_deleted($orig);
    echo "---\n";
    $this->_added($closing);
  }
}


/**
 *  Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
 *
 */

define('NBSP', "\xC2\xA0");     // utf-8 non-breaking space.

class _HWLDF_WordAccumulator {
  function _HWLDF_WordAccumulator () {
    $this->_lines = array();
    $this->_line = '';
    $this->_group = '';
    $this->_tag = '';
  }

  function _flushGroup ($new_tag) {
    if ($this->_group !== '') {
    if ($this->_tag == 'mark')
      $this->_line .= '<strong>'.$this->_group.'</strong>';
    else
    $this->_line .= $this->_group;
  }
    $this->_group = '';
    $this->_tag = $new_tag;
  }

  function _flushLine ($new_tag) {
    $this->_flushGroup($new_tag);
    if ($this->_line != '')
      $this->_lines[] = $this->_line;
    $this->_line = '';
  }

  function addWords ($words, $tag = '') {
    if ($tag != $this->_tag)
      $this->_flushGroup($tag);

    foreach ($words as $word) {
      // new-line should only come as first char of word.
      if ($word == '')
        continue;
      if ($word[0] == "\n") {
        $this->_group .= NBSP;
        $this->_flushLine($tag);
        $word = substr($word, 1);
      }
      assert(!strstr($word, "\n"));
      $this->_group .= $word;
    }
  }

  function getLines() {
    $this->_flushLine('~done');
    return $this->_lines;
  }
}

class WordLevelDiff extends MappedDiff
{
  function WordLevelDiff ($orig_lines, $closing_lines) {
    list ($orig_words, $orig_stripped) = $this->_split($orig_lines);
    list ($closing_words, $closing_stripped) = $this->_split($closing_lines);


    $this->MappedDiff($orig_words, $closing_words,
              $orig_stripped, $closing_stripped);
  }

  function _split($lines) {
    // FIXME: fix POSIX char class.
#    if (!preg_match_all('/ ( [^\S\n]+ | [[:alnum:]]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
    if (!preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
              implode("\n", $lines),
              $m)) {
      return array(array(''), array(''));
    }
    return array($m[0], $m[1]);
  }

  function orig () {
    $orig = new _HWLDF_WordAccumulator;

    foreach ($this->edits as $edit) {
      if ($edit->type == 'copy')
        $orig->addWords($edit->orig);
      elseif ($edit->orig)
        $orig->addWords($edit->orig, 'mark');
    }
    return $orig->getLines();
  }

  function closing () {
    $closing = new _HWLDF_WordAccumulator;

    foreach ($this->edits as $edit) {
      if ($edit->type == 'copy')
        $closing->addWords($edit->closing);
      elseif ($edit->closing)
        $closing->addWords($edit->closing, 'mark');
    }
    return $closing->getLines();
  }
}

/**
 * "Unified" diff formatter.
 *
 * This class formats the diff in classic "unified diff" format.
 */
class UnifiedDiffFormatter extends DiffFormatter
{
    function UnifiedDiffFormatter($context_lines = 4) {
        $this->leading_context_lines = $context_lines;
        $this->trailing_context_lines = $context_lines;
    }

    function _block_header($xbeg, $xlen, $ybeg, $ylen) {
        if ($xlen != 1)
            $xbeg .= "," . $xlen;
        if ($ylen != 1)
            $ybeg .= "," . $ylen;
        return "@@ -$xbeg +$ybeg @@\n";
    }

    function _added($lines) {
        $this->_lines($lines, "+");
    }
    function _deleted($lines) {
        $this->_lines($lines, "-");
    }
    function _changed($orig, $final) {
        $this->_deleted($orig);
        $this->_added($final);
    }
}

/**
 *  Wikipedia Table style diff formatter.
 *
 */
class TableDiffFormatter extends DiffFormatter
{
  function TableDiffFormatter() {
    $this->leading_context_lines = 2;
    $this->trailing_context_lines = 2;
  }

  function _pre($text){
    $text = htmlspecialchars($text);
    $text = str_replace('  ',' &nbsp;',$text);
    return $text;
  }

  function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
    global $lang;
    $l1 = $lang['line'].' '.$xbeg;
    $l2 = $lang['line'].' '.$ybeg;
    $r = '<tr><td class="diff-blockheader" colspan="2">'.$l1.":</td>\n" .
      '<td class="diff-blockheader" colspan="2">'.$l2.":</td></tr>\n";
    return $r;
  }

  function _start_block( $header ) {
    print( $header );
  }

  function _end_block() {
  }

  function _lines( $lines, $prefix=' ', $color="white" ) {
  }

  function addedLine( $line ) {
    $line = str_replace('  ','&nbsp; ',$line);
    return '<td>+</td><td class="diff-addedline">' .
      $line.'</td>';
  }

  function deletedLine( $line ) {
    $line = str_replace('  ','&nbsp; ',$line);
    return '<td>-</td><td class="diff-deletedline">' .
      $line.'</td>';
  }

  function emptyLine() {
    //$line = str_replace('  ','&nbsp; ',$line);
    return '<td colspan="2">&nbsp;</td>';
  }

  function contextLine( $line ) {
    $line = str_replace('  ','&nbsp; ',$line);
    return '<td> </td><td class="diff-context">'.$line.'</td>';
  }

  function _added($lines) {
    foreach ($lines as $line) {
      print( '<tr>' . $this->emptyLine() .
        $this->addedLine( $line ) . "</tr>\n" );
    }
  }

  function _deleted($lines) {
    foreach ($lines as $line) {
      print( '<tr>' . $this->deletedLine( $line ) .
        $this->emptyLine() . "</tr>\n" );
    }
  }

  function _context( $lines ) {
    foreach ($lines as $line) {
      print( '<tr>' . $this->contextLine( $line ) .
        $this->contextLine( $line ) . "</tr>\n" );
    }
  }

  function _changed( $orig, $closing ) {
    $diff = new WordLevelDiff( $orig, $closing );
    $del = $diff->orig();
    $add = $diff->closing();

    while ( $line = array_shift( $del ) ) {
      $aline = array_shift( $add );
      print( '<tr>' . $this->deletedLine( $line ) .
        $this->addedLine( $aline ) . "</tr>\n" );
    }
    $this->_added( $add ); # If any leftovers
  }
}


//Setup VIM: ex: et ts=2 enc=utf-8 :
